The present invention relates generally to printer-plotter systems and, more particularly, to dot-matrix thermal printer-plotters. Thermal printer-plotters are known which have thermal resistive elements (dots) arranged in matrix form, each column and each row of matrix having multiple resistive elements.
However, to form the vertical portion of a character, the column elements of the matrix are sometimes energized simultaneously. This often results in non-uniformity of contrast between portions of the character formed by a given number of the matrix elements energized simultaneously and other portions of the character formed by a different number of simultaneously energized elements. This non-uniformity in contrast is caused by parasitic losses, such as are produced by a battery return lead and resistance, which reduce the amount of powder supplied to each element as a function of the number of simultaneously energized elements.
To avoid this problem of non-uniformity in contrast associated with simultaneously energized elements, a printer-plotter with individually energizable print and plot elements is needed. Also, for purposes of compactness and simplicity, the elements should be arranged in a single print-plot head in such a manner that, to print a selected character, the same elements may be used to print the character in one direction as to print the character in other directions.